1. Field of the Invention
The present invention relates to a coating film processing method and coating film processing apparatus for processing a coating film formed on the surface of a substrate, such as a semiconductor substrate, to prepare for an immersion light exposure process arranged to perform light exposure through a liquid.
2. Description of the Related Art
In the process of manufacturing semiconductor devices, photolithography techniques are used for forming circuit patterns on semiconductor wafers. Where a circuit pattern is formed by use of photolithography, the process steps are performed, as follows. Specifically, a resist liquid is first applied to a semiconductor wafer to form a resist film. Then, the resist film is irradiated with light to perform light exposure on the resist film in accordance with the circuit pattern. Then, the resist film is subjected to a developing process.
In recent years, the integration degree of semiconductor devices becomes increasingly higher to improve the operation speed and so forth. Accordingly, photolithography techniques are required to increase the miniaturization level of circuit patterns formed on semiconductor wafers. As a photolithography technique for realizing a high resolution of a 45-nm node level, there has been proposed the following immersion light exposure (for example, see U.S. Patent Application Publication No. US 2006/0231206 A1). In this immersion light exposure, a liquid, such as purified water, having a refractive index higher than air is supplied between the semiconductor wafer and light exposure projection lens. The wavelength of light radiated from the projection lens is shortened by means of the refractive index of the liquid, so that the line width obtained by the light exposure is decreased.
In the immersion light exposure, a resist film is sometimes covered with a liquid repellent protection film formed thereon to prevent the liquid from being impregnated into the resist film and to prevent resist components from being dissolved into the liquid. Further, for example, an anti-reflective coating is sometimes disposed below the resist film. In general, where a film, such as a resist film, is formed on the wafer surface, a coating liquid is first applied to form a coating film, and a solvent is then supplied onto the edge portion to perform an edge-cutting process. During this edge-cutting process, process defects, such as sags, disorders, and/or humps, can be easily generated. Where films are stacked one on the other on the wafer surface, as described above, process defects can be more easily generated at the edge portion.
If process defects are generated at the edge portion, when the liquid immersion head of an immersion light exposure apparatus is traveling across the wafer edge portion, stresses are applied to the edges (end faces) of films formed on the wafer, thereby causing film peeling. This film peeling may produce deposits on the wafer surface and generate development defects, and/or may contaminate the lens of the immersion light exposure apparatus.
In order to solve these problems, cleaning may be performed on the edge portion of a coating film to prevent film peeling, after the coating film formation and edge-cutting and before the immersion light exposure. In this case, however, the apparatus structure and process steps are complicated, because the edge-cutting is followed by a soft baking process, in general.